JP2002275580A - Antifriction bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antifriction bearing in which deformation at heat treatment, such as hardening, is reduced. SOLUTION: In the deep groove ball bearing having an outer race 1, an inner race 2 and a plurality of balls 3 rollably provided between the outer race 1 and the inner race 2, the outer race 1 and the inner race 2 are constituted of steel which contains 0.7-1.1% carbon, <=1.0% silicon, <=1.5% manganese, <=8.0% chromium and <=2.0% molybdenum and has >=250 mm DI value. Moreover, the maximum value of the thickness of the outer race 1 and the inner race 2 is made to 3 mm, and the outside diameter of the outer race 1 is made to 30 mm. Further, the outer race 1 and the inner race 2 are subjected to hardening where heating is done in vacuum and cooling is done in inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing, and more particularly, to a rolling bearing which undergoes little deformation during heat treatment such as quenching.

[0002]

2. Description of the Related Art Conventionally, a bearing ring of a rolling bearing has a maximum thickness (a radial distance between an inner peripheral surface and an outer peripheral surface in the case of a radial bearing) of 15 mm or less.
A hardened and tempered JIS SUJ2 was used. Cooling in quenching has been performed by charging in oil (oil quenching) or charging in salt (salt quenching) so that the core of the race is hardened.

[0003]

However, in the above-described oil quenching, since the cooling of the bearing ring is not always performed uniformly, there is a problem that the deformation may be large. Another problem is that it takes time to remove the quenching oil in the washing step. On the other hand, although the above-described salt quenching has less deformation due to heat treatment than oil quenching, it has a problem that it takes time to remove the salt in cleaning and a problem that rust is easily generated on the raceway. .

[0004] Therefore, an object of the present invention is to solve the problems of the prior art and to provide a rolling bearing with small deformation during heat treatment such as quenching.

[0005]

In order to solve the above problems, the present invention has the following arrangement. That is, the rolling bearing according to claim 1 of the present invention is a rolling bearing including an outer ring, an inner ring, and a plurality of rolling elements disposed so as to freely roll between the outer ring and the inner ring. At least one of the inner ring and the outer ring contains 0.7-1.
1%, 1.0% or less of silicon, 1.5% or less of manganese, 8.0% or less of chromium, 2.0% or less of molybdenum, and a steel having a DI value of 250 mm or more. , Wherein the maximum value of the thickness is 3 mm or less.

A rolling bearing according to a second aspect of the present invention is the rolling bearing according to the first aspect, wherein the outer diameter of the outer ring is 30 mm or less. Further, the rolling bearing according to claim 3 of the present invention is the rolling bearing according to claim 1 or 2, wherein the outer ring and the inner ring, which are made of the steel, are cooled by performing heating in a vacuum. In an inert gas.

Here, the above-mentioned DI value (Jomini index) will be described. When the diameter of the material to be quenched is small, quenching is performed up to the core to increase the hardness, but when the diameter is larger than a certain degree, the part is not fully quenched and the part that does not turn into martensite increases. Therefore, the hardness of the core of the hardened material tends to rapidly decrease as the diameter increases. However, if the hardenability of the material is excellent, even a material having a larger diameter can be completely quenched (that is, the hardness of the core after quenching is high).

[0008] The DI value is one parameter representing the hardenability, and indicates the critical value of the diameter at which the core is hardened. In other words, a material having a higher DI value has better hardenability. Such a DI value can be measured, for example, by a steel hardenability test method specified in JIS G0561. Regarding the DI value, various defining formulas have been obtained through experiments and the like.

In the present invention, AISI (American I
The DI value calculated by the following equation defined by Ron and Steel Institute) is used. DI value = (0.311 × C% ^0.498 ) × (0.7 × Si
% + 1) × (3.33 × Mn% + 1) × (2.16 × C
r% + 1) Since the unit of the DI value obtained by this equation is inches, the present invention uses the DI value converted to millimeter units. C% in the following equation is the concentration of carbon contained in the steel, and is Si%, Mn%, Cr%
Is also the concentration of silicon, manganese and chromium.

In the present invention, the race is made of steel having a DI value of at least 250 mm and excellent in hardenability, and the thickness of the race made of the steel (in the case of a radial bearing, the inner peripheral surface is The maximum value of the distance in the radial direction from the outer peripheral surface is limited to 3 mm or less so that quenching can be easily performed to the core. Hardening can be performed up to the part.

As a result, the amount of deformation due to the heat treatment can be greatly reduced, and a raceway (rolling bearing) with good roundness can be manufactured. As a result, it is possible to shorten the processing time of the grinding process of the bearing ring,
Processing costs can be reduced. In addition, since it is not necessary to use quenching oil or salt as a coolant in the cooling of quenching, a post-cleaning step for removing the coolant is not required.

Further, foreign matter such as dust mixed in the quenching oil does not adhere to non-ground portions such as seal grooves. Therefore, the acoustic quality of the rolling bearing is excellent. DI
If the value is less than 250 mm or the maximum value of the thickness of the bearing ring is more than 3 mm, when gas cooling is adopted for quenching, the core is not quenched and the hardness is insufficient. In some cases, deformation during quenching increases, and there is a possibility that a raceway having sufficient roundness may not be obtained.

Further, in the rolling bearing of the present invention, it is preferable that the outer diameter of the outer race be 30 mm or less. If the outer diameter of the outer ring is more than 30 mm, deformation during quenching is increased, and sufficient roundness may not be obtained. Further, in the rolling bearing of the present invention, it is preferable that the bearing ring made of the steel is subjected to quenching in which heating is performed in a vacuum and cooling is performed in an inert gas.

By performing the quenching heating in a vacuum, foreign matters adhering to the bearing ring can be reduced, which is particularly effective when extremely high sound quality is required such as a rolling bearing for HDD. In addition, examples of the inert gas include a nitrogen gas and a rare gas. Next, each element contained in the steel according to the present invention will be described.

(1) Carbon (C) The content of C must be 0.7 to 1.1%. C
Is less than 0.7%, the hardness (H
RC58) cannot be obtained, and if the content exceeds 1.1%, coarse carbides are formed and the rolling life may be reduced.

(2) Silicon (Si) The content of Si must be 1.0% or less. Si is inevitably contained in an amount of about 0.01% or more from the deoxidizing agent at the time of steel making. However, if it exceeds 1.0%, cold workability is impaired. (3) Manganese (Mn) The content of Mn needs to be 1.5% or less.

Mn is an element necessary for improving the hardenability, but if contained in excess of 1.5%, the deformation resistance increases. (4) Chromium (Cr) The content of Cr needs to be 8.0% or less. Cr is an element necessary for improving hardenability and abrasion resistance, but if it is less than 0.9%, hardenability and abrasion resistance become insufficient, and it exceeds 8.0%. And a large amount of eutectic carbides are formed, and workability is reduced.

(5) Molybdenum (Mo) The content of Mn must be 2.0% or less. Mo is added to improve hardenability, but if it exceeds 2.0%, the effect of improving hardenability decreases.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a rolling bearing according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial sectional view showing the structure of a single-row deep groove ball bearing which is an embodiment of the rolling bearing of the present invention. The deep groove ball bearing (J
IS call number: 6200, outer diameter 30mm, inner diameter 10m
m, width 9 mm) includes an outer ring 1, an inner ring 2, a plurality of balls 3 rotatably disposed between the outer ring 1 and the inner ring 2, and a crown-shaped retainer (not shown) for holding the balls 3. , Is comprised.

The outer ring 1 and the inner ring 2 contain carbon in the range of 0.7 to 1.0.
It is composed of steel containing 1% or less of silicon, 1.0% or less of manganese, 1.5% or less of manganese, 8.0% or less of chromium, and 2.0% or less of molybdenum and having a DI value of 250 mm or more. . The maximum value of the thickness of the outer ring 1 and the inner ring 2, that is, the maximum value of the distance in the radial direction between the inner peripheral surface and the outer peripheral surface of the outer ring 1 and the inner ring 2 is 3 mm.

The deep groove ball bearing according to this embodiment has the following features.
The outer ring 1 and the inner ring 2 are subjected to quenching in which heating is performed in a vacuum and cooling is performed in an inert gas such as a nitrogen gas or a rare gas. A deep groove ball bearing as described above has a DI value of 25
Outer ring 1 and inner ring 2 made of steel with excellent hardenability of 0 mm or more
Is constituted, and the maximum value of the thickness of the outer ring 1 and the inner ring 2 is set to 3 mm so that quenching is easily performed to the core. Therefore, even if gas cooling with a low cooling rate is adopted for quenching,
Hardened to the heart.

Further, since the gas cooling is employed, the deformation of the outer ring 1 and the inner ring 2 due to the heat treatment is small, and the roundness of the outer ring 1 and the inner ring 2 is good. As a result, the processing time of the grinding process of the outer ring 1 and the inner ring 2 can be shortened, so that the processing cost is low. Further, since the quenching is performed in a vacuum, there is little foreign matter attached to the outer ring 1 and the inner ring 2. Therefore, it can be suitably used especially for applications requiring extremely high acoustic quality, such as rolling bearings for HDDs.

Further, since no quenching oil or salt is used as a coolant in the cooling of the quenching, a post-cleaning step for removing the coolant is not required. Furthermore, foreign substances such as dust mixed in the quenching oil do not adhere to non-ground portions such as seal grooves. Therefore, the sound quality of the deep groove ball bearing is excellent. Further, in the deep groove ball bearing of the present embodiment, since the outer diameter of the outer ring 1 is 30 mm, deformation during quenching is small and sufficient roundness is obtained. Therefore, when the seal is attached, the deformation of the seal is small, so that excellent sealing performance can be maintained.

The present embodiment is an example of the present invention, and the present invention is not limited to the present embodiment. For example, in the present embodiment, both the outer ring 1 and the inner ring 2 are made of the steel, but only one of them may be made of the steel. Further, in the present embodiment, the deep groove ball bearing has been described as an example of the rolling bearing. However, the rolling bearing of the present invention can be applied to various kinds of other rolling bearings. For example, there are radial rolling bearings such as angular ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust rolling bearings such as thrust ball bearings and thrust roller bearings.

However, in the case of a thrust type rolling bearing, the thickness of the outer ring and the inner ring is the height of the washer. (Example) Next, a description will be given of the results of studies on hardenability (hardness) and deformation when an annular member having a shape similar to the outer race is subjected to heat treatment.

The steel constituting the annular member is of four types (Examples 1 to 3 and Comparative Examples) having the composition and DI value as shown in Table 1. The steel of Example 1 is SUJ5, the steel of Example 2 is SKD12, and the steel of Comparative Example is SUJ2.
Further, the shape of the annular member has an outer diameter of 30 mm and a width of 9 m.
m, 4 types with thickness of 1, 2, 3, 5 mm
00 is a shape corresponding to the outer ring of a deep groove ball bearing.

[0027]

[Table 1]

Such an annular member was quenched under heat treatment conditions shown in Table 1 and thereafter tempered.
More specifically, an annular member is placed in a heating chamber of an all-case furnace, and a nitrogen atmosphere (preferably, 1 to 3 vol% (less than explosion limit) of hydrogen is mixed in order to make a weak reducing atmosphere). To the temperature shown in Table 1,
Hold for 0 minutes. Thereafter, the annular member was moved to a cooling chamber, and cooled and quenched while blowing nitrogen gas with a stirring fan. Then, the quenched annular member was transferred to a thermostat and kept at 160 ° C. for 2 hours to perform tempering.

The cooling of the quenching was performed using nitrogen gas as a coolant (gas cooling) as described above for each of the annular members of the working example, whereas the cooling of the annular members of the comparative example was performed in oil. This was performed by immersion in Next, with respect to the obtained annular member, the Vickers hardness Hv at a substantially central portion (core portion) of the cross section was measured. Table 2 shows the results.

[0030]

[Table 2]

As can be seen from the results in Table 2, in the case of the comparative example, the hardenability of the steel is insufficient (the DI value is less than 250 mm), so that even when the thickness is 1 mm, the hardening is applied to the core. Hardness Hv 660 required for rolling bearings
(HRC 58.3). In contrast, in the case of Example 1, when the thickness was as large as 5 mm, quenching was not applied to the core, but up to 3 mm, quenching was applied to the core. Hv700 or more.

In Examples 2 and 3, since the hardenability of the steel is excellent, even when the thickness is as large as 5 mm, the hardening is applied to the core and the hardness is Hv 700 or more. That was enough. Next, with respect to the annular members of Example 2 and Comparative Example, the degree of deformation due to the heat treatment was evaluated by measuring the roundness after quenching and tempering. For this evaluation, eleven kinds of annular members having an outer diameter of 8 to 150 mm were newly prepared (see Table 3), subjected to the same heat treatment as described above, and evaluated together with those having an outer diameter of 30 mm. In addition, about each annular member, three kinds of thickness 1, 2, and 3 mm were prepared. Table 3 shows the evaluation results.

[0033]

[Table 3]

Regarding the comparative example, the circularity of all the annular members exceeded 0.020 mm regardless of the outer diameter and the thickness. If the roundness exceeds 0.020 mm, the processing time of the grinding process cannot be reduced, and the processing cost cannot be reduced. On the other hand, in the case of the second embodiment,
As long as the outer diameter was 30 mm or less, the roundness was 0.020 mm or less in any thickness. Therefore, the processing time of the grinding step can be reduced, and the processing cost can be reduced.

However, when the outer diameter was 40 mm or more, the roundness exceeded 0.020 mm. From the above results, if the annular member is made of steel having an excellent hardenability having a DI value of 250 mm or more, the maximum value of the thickness is 3 mm or less, and further, if the outer diameter is 30 mm or less, the hardening of Even if gas cooling with a low cooling rate is used for cooling, quenching can be performed up to the core, and the hardness of the core can be equal to or higher than Hv660, which is the hardness required for the rolling bearing. In addition, the deformation during quenching can be reduced, so
An annular member having a sufficient roundness of 020 mm or less can be obtained.

[0036]

As described above, the rolling bearing according to the first aspect of the present invention comprises a raceway made of a steel having an excellent hardenability having a DI value of 250 mm or more. Since the maximum value of the thickness is 3 mm or less, even when gas cooling with a low cooling rate is employed for quenching, quenching can be performed up to the core. In addition, since the amount of deformation due to the heat treatment is small, the roundness is good.

Further, the rolling bearing according to claim 2 of the present invention,
Since the outer diameter of the outer ring is 30 mm or less, deformation during quenching is small, and sufficient roundness is obtained. Further, in the rolling bearing according to claim 3 of the present invention, the bearing ring made of steel is subjected to quenching in which heating is performed in a vacuum and cooling is performed in an inert gas. There is no need to use quenching oil or salt as a coolant in the above. Therefore, a post-cleaning step for removing the coolant is not required.

Further, since the heating for quenching is performed in a vacuum and the cooling is performed in an inert gas, the amount of foreign matter adhering to the bearing ring is small. Therefore, the acoustic quality of the rolling bearing is excellent.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a structure of a single-row deep groove ball bearing which is an embodiment of a rolling bearing of the present invention.

[Explanation of symbols]

 1 outer ring 2 inner ring 3 balls

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Claims (3)

[Claims] 1. A rolling bearing comprising an outer ring, an inner ring, and a plurality of rolling elements rotatably disposed between the outer ring and the inner ring, at least one of the inner ring and the outer ring. Contains 0.7 to 1.1% of carbon, 1.0% or less of silicon, 1.5% or less of manganese, 8.0% or less of chromium, 2.0% or less of molybdenum, and a DI value of A rolling bearing comprising a steel of 250 mm or more and having a maximum thickness of 3 mm or less. 2. The rolling bearing according to claim 1, wherein the outer diameter of the outer ring is 30 mm or less. 3. An outer ring and an inner ring made of the steel are hardened by heating in a vacuum and cooling in an inert gas. The rolling bearing according to claim 1 or 2.